While chicken cooks, in a second large skillet over medium to medium high heat, add oil and butter. To melted butter, add onion, carrots, celery, and mushrooms, adding veggies to the pan as you chop them. Add bay leaf and season veggies with thyme, salt and pepper. Saute 10 minutes, stirring frequently. Add flour and cook another minute. Whisk in reserved 2 cups of stock forming a sauce around veggies. Stir in cooked chicken pieces, parsley and peas. Transfer the mixture to a large casserole, oval or rectangular. Open the biscuits and arrange them, edges touching, in a layer across the top of the casserole. Bake 8 to 10 minutes until biscuits are golden brown, then serve.